Field of the Invention
One or more embodiments of the invention are related to the field of optical systems for producing views of a display, such as for example stereoscopic views or views that vary based on a user's location. One or more embodiments are also related to the field of tracking systems for heads or eyes. More particularly, but not by way of limitation, one or more embodiments of the invention enable a trackable glasses system that provides multiple views of a shared display.
Description of the Related Art
There are various methods known in the art for creating a 3D stereoscopic image. Most commonly these include, but are not limited to shutter glasses, passively polarized glasses, and anaglyph glasses. The stereoscopic image may present on a flat panel, projection or other display medium. These glasses discriminate between first and second images and coordinate with the display medium to present the corresponding image to the correct eye. In this way, a stereoscopic image or a dual view image may be presented.
In addition to or instead of presenting different images to different eyes of a single user, in many situations it is useful to present different images to different users. While shutter glasses may be used for this purpose, the speed of the shutter lenses and the speed of switching the display panel limits the number of concurrent users. There is a need for a system that supports a larger number of views of a single shared display.
In many situations, it is also useful or necessary to track the position and orientation of each user's head or eyes, for example to present an image to that user that corresponds to the user's viewpoint. Systems that are used to track the eyes in order to produce 3D stereoscopic images vary, but there are no inexpensive methods currently in use. Examples of tracking systems known in the art include the ZSpace system, the TrackIR system by Naturalpoint, and the Microsoft Kinect system. Each of these devices has limitations.
ZSpace employs a tablet with two custom cameras that track glasses with 5 tracking blobs on the glasses. A version of this method is described in US 2013/0128011. The devices are expensive; at the time of this writing the minimum order is ten units at a price between $22,000 to $47,000. This is cost prohibitive for the average user.
The TrackIR made by Naturalpoint employs infrared (IR) lights mounted on headgear. The least expensive version is currently sold for about $200. The IR lights are difficult to attach correctly and the system is difficult to employ correctly.
The Microsoft Kinect employs a method of structured light where patterns of IR light are shined on an object and the changes in the pattern due to the shape of the object are used to determine the 3D structure and location of the object. These systems may employ one or more sources of light and one or more cameras for viewing. The Kinect has the ability to face track, but results are unreliable. The current software is not optimized for when glasses are worn and it loses tracking easily. In addition, the cost is around $200 for a Kinect.
Most modern computers already come equipped with a camera at no extra cost. Those that do not may be equipped with an inexpensive camera that transfers data via the USB port. A user would prefer to use the camera that came with their computer rather than purchase an expensive accessory in order to create real world 3D stereoscopy. However, these inexpensive cameras do not have depth sensing.
A series of markers or blobs on the glasses may be used to mark locations on the glasses. The distance between the blobs as measured by camera angle may not yield accurate information because the head may be turned from the camera in several axes. This changes the distance between the blobs as seen by the camera. For example, turning the head to either side by thirty degrees could result in a fifty percent error in the distance between two blobs located horizontally from one another. This results in a corresponding error in tracking location.
US 2010/0103516 describes a head tracking system employing reflective blobs that fails to take into account the error associated with turning the head along various axes. It describes changing the polarization of these blobs by means of a retarder. The fact that these reflective blobs may have their polarization altered has no bearing on this error.
Various methods have been proposed to track eyewear, most involving markers or blobs on a surface. The shape of these systems varies with the angular relationship of the surface to the camera(s). This makes it difficult to track said eyewear accurately with inexpensive cameras.
Therefore, it would be highly desirable to have a system and/or method that uses one or more inexpensive cameras to track the head or the eyes, and that also negates the error due to tilting or turning of the head.
Another current problem involves manipulation of the 3D stereoscopic imagery. Z-space currently employs a pointer that is tracked and provides a 3D line that is drawn from the tip of the pointer by the software and is employed to manipulate stereoscopic images. The pointer does not produce a beam, but rather the beam is presented as a 3D stereoscopic image that gives the impression of being generated from the pointer. This requires a complex system of two precisely positioned cameras to precisely track the pointer. Thus, it cannot be used on current common systems that have only one camera. In addition, one hand is used to hold the tablet device and the other is used to manipulate the pointing device. This leaves no hands free to manipulate other controls. It would be desirable to have a method of pointing and of manipulating imagery that requires only a single camera, and that does not require a separate pointing device.
For at least the limitations described above there is a need for a trackable glasses system that provides multiple views of a shared display.